USDA hardiness zones in Montana
| Zone | Avg. extreme minimum | ZIP codes | Example cities |
|---|---|---|---|
| Zone 3b | −35 to −30°F | 26 | Havre |
| Zone 4a | −30 to −25°F | 74 | Sidney |
| Zone 4b | −25 to −20°F | 116 | Great Falls, Miles City, Lewistown |
| Zone 5a | −20 to −15°F | 90 | Billings, Bozeman, Butte, Helena |
| Zone 5b | −15 to −10°F | 29 | Missoula, Kalispell, Hamilton |
| Zone 6a | −10 to −5°F | 28 | Polson |
| Zone 6b | −5 to 0°F | 1 | — |
Growing zone and frost dates by city
| City | Zone | Frost dates |
|---|---|---|
| Billings | 5a (−20 to −15°F) | Billings frost dates |
| Missoula | 5b (−15 to −10°F) | Missoula frost dates |
| Great Falls | 4b (−25 to −20°F) | Great Falls frost dates |
| Bozeman | 5a (−20 to −15°F) | Bozeman frost dates |
| Butte | 5a (−20 to −15°F) | Butte frost dates |
| Helena | 5a (−20 to −15°F) | Helena frost dates |
| Kalispell | 5b (−15 to −10°F) | Kalispell frost dates |
| Belgrade | 5a (−20 to −15°F) | Belgrade frost dates |
| Anaconda | 5a (−20 to −15°F) | Anaconda frost dates |
| Whitefish | 5a (−20 to −15°F) | Whitefish frost dates |
| Livingston | 5a (−20 to −15°F) | Livingston frost dates |
| Havre | 3b (−35 to −30°F) | Havre frost dates |
| Miles City | 4b (−25 to −20°F) | Miles City frost dates |
| Laurel | 5a (−20 to −15°F) | Laurel frost dates |
| Sidney | 4a (−30 to −25°F) | Sidney frost dates |
| Lewistown | 4b (−25 to −20°F) | Lewistown frost dates |
| Columbia Falls | 5a (−20 to −15°F) | Columbia Falls frost dates |
| Polson | 6a (−10 to −5°F) | Polson frost dates |
| Hamilton | 5b (−15 to −10°F) | Hamilton frost dates |
Frequently asked questions
What growing zone is Montana in?
Montana’s ZIP codes span USDA zones 3b to 6b, and 4b is the most common. Zones vary with elevation and distance from water, so check your own ZIP code.
When should I plant?
Hardiness zones are about winter cold, not planting dates. For timing, use the last spring frost date for your city on our Montana frost dates page.